This invention relates to rod couplings, such as those used for pumping units in oil field production.
In a typical oil field, oil is pumped from the well by a pumping unit positioned at the surface. A typical pumping unit includes a motor driven reciprocating walking beam with one end positioned over the well and connected to a string of sucker rods in the bore by a bridle ring. There may be several thousand feet of sucker rods in the well, which rods are joined by sucker rod couplings.
The pumping string, comprising sucker rods and rod couplings, is reciprocated inside the well casing and since the couplings are of greater diameter than the rods, there is extensive abrasion of the couplings in the pumping operation. This rubbing between coupling and the inner surface of the casing also causes damage to the casing pipe.
Typical sucker rod couplings are formed of high quality steel with a cylindrical exterior and a central axial threaded bore. If desired, parallel wrench flats may be provided on the exterior for use in making up the sucker rod string.
It is an object of the present invention to provide a new and improved rod coupling which will have a substantially increased useful operating life in comparison with the conventional coupling now in use. A further object is to provide such a coupling which will substantially reduce the wear on the interior of the casing of a well.
It is a particular object of the invention to provide a rod coupling having the outer surface completely enclosed in a flexible abrasive resistant plastic coating, preferably a thermoplastic hydrourethane polymer.
These and other objects, advantages, features and results will more fully appear in the course of the following description.